As some of you might know, I am in the process of designing my own dream bike, a monocoque carbon all purpose road bike. I have ridden most of the top brands over 20 years and it’s time I created my own.

This is like the ultimate custom bike experience.

As my fellow weenies have not failed to provide me with inspirations (Cippo, Berk, Andy2, Madcow…too many to list) as well as a tremendous wealth of information over the years, I thought I’d share with you my joy in the design process.

I’d appreciate any thoughts you may have on the design. Pls be as critical as you can.

I understand some weenies are actual industry heavyweights (oops), and many more are experts in engineering and other sciences, so I am expecting this exercise to be extremely educational as well.

My goal -- a well rounded all purpose road bike. It will have some aero features but will not be called an “Aero” bike like the S5, Venge, etc.

Why so? I understand many manufacturers are making “aero” bikes as well as a “climbing” bikes (somehow they don’t call them that any more, but the chase for light weight is still on). lightweight envelopes are being pushed with R5CA, Zero7, BH Superlight, Evo, etc., all with minimal aero features. My problem is, and I am sure many of you share, that you can’t have a support vehicle change your bike at the foot of a climb. You are generally stuck with “one” bike per ride.

The way I see it, Cervelo and the like are trying to show they CAN achieve something remarkable but they have not necessarily figured out what would be “THE” bike if you can only have one. That’s why we see Thor on the 1400g S5 while DZ, the tt expert on the 700g R5CA, with disk wheels nonetheless, but the square (sorry, squoval) tubing or the big voids between seattube and rear wheel is simply not taken care of;-)

Therefore, this bike will be an all purpose bike with some aero features (which will be explained later).

I have thought long and hard about this one. Been doing a lot of research and met with many manufacturers in the area. In fact I also ran into a few Chinarello makers. Most of them are quite unreliable. It's really amazing how many "big brands" are being knocked off.

I ended up going with a manufacturer that I found to be very solid. They have built carbon bikes for several brands people are familiar with but out of respect for each other (as well to comply with confidentiality in the contract), I will not discuss further which company this is, and whose bikes they also build.

They tend to actually over build their products a bit but with the vivid images of Chinarello riders' face plants, that might be a good thing. We shall see how it comes out in the end. 900g is the aim for a size 53.

BTW, here is a little example of what's being contemplated. Won't be a weenie but should be pretty solid (hoping to get it within 140g).

The arguments have been made many times, with the current trend disfavoring ISP slightly. That said, I still believe if you do not require a ton of adjustability, then it can be quite nicely (and lightly) executed.

Too many times arguments are made based on resale value. Yet few seem to make that argument against cutting forks (sorry, DJ ).

Here are the options I have.

Somehow, I find an internal seatpost much more pleasing aesthetically (plus if you have bigger thighs, you'd appreciate this design, compared to a big clamp around some 37mm thick mast).

But I do not like the idea of a bolt through the mast.

So I start off from this design. An FSA 200g boat anchor.

Fortunately, the beauty of this design, is that you do NOT need the friction on the mast to maintain it's height. All you need is that it won't pull out or twist around in the mast. Hence, some optimization on the design is imperitive.

Too many times arguments are made based on resale value. Yet few seem to make that argument against cutting forks (sorry, DJ ).

HA! Perhaps because it's a moot point? Forks are easier to replace than entire frames. Fork too short? Replace it. ISP cut too short? Well... replace the frame? What's the point of the sale then? Frames and forks are separate components, often paired together but separate nonetheless. You buy a bike for the frame, not the fork. Forks are replaceable. ISPs are still shite.

I really like what A2J is doing on their frame. Especially the cable routing. If its a one off just for you I think an ISP is a great idea. Check out the seatpost set up on the Mercxk EMX 7. Depending on your component choice you can do some really cool integration.

Prend -- I hear you loud and clear. I suppose it's all relative. I still remember the days when a C40's Star fork cost my monthly salary. Plus ISPs generally come with SOME adjustability while forks have none (except for spacer on top of stem).

But yes, the adjustability issue is indeed acknowledged.

I have 3 options regarding this issue:

1. bite the bullet and have no adjustability at all. If I go to a thinner shoe, then I am screwed. 2. do what most people do and offer a small 20-30mm adjustability. But improve on the topper design to save some weight. One direction is going with a bit thinner topper. I believe most of today's ISP mast is overbuilt anyway, as the biggest load is in the cluster area and not at the topper. Assuming sound mechanical installation, this area takes little load. My struggles is how small a bolt I should adopt. 3. the most liekly solution is offer a longer version topper that provides 30mm of additional lee way at a 15-20g penalty. Trek has done this I blieve. This should resolve 99% of the problems.

Coloclimber, as you suggested, the EM7 is indeed quite nice. That said, it uses the FSA expander-type seatpost which is grossly overbuilt and very heavy.

So I am hoping my bike will be a bit lighter.

Regarding whether this will become commercial, I am still undecided (leaning towards yes). Let's see what comes out first though.

Having seen too many designs over the years, I can't help thinking a lot of the designs out there in the name of "engineering" are nothing but easthetic in nature or for marketing purposes (I don't like to use the word "gimmick" because there is a lot more to this sport than adding XX seconds to your next 40km TT).

Square tubing, HP chainstays, Zerts, to name a few. Or whatever this BMC design is called.

Therefore, this time around, I will try to use more round shapes, continuous curves, unless I am absolutely sure a departure serves any real purpose. This is hardly new (Parlee, Crumpton, etc...) but it will be interesting to see how it blends with the semi aero features.

For starter, now that I have decided to use ISP, the ISP mast will be aero but I will depart from the typical airfoil spotted on Pinarello/Merckx/TIme RXR/and really pretty much every aero bike, which has a round front portion but "V" trailing edge.

We all know wide flat surface isn't known to be very stiff, and counterintuitively, the V shaped tubing may not be necessarily that aerodynamic either. Interestingly, the wheel industry, whose livlihood pretty much depends on aerodynamics, are going away from "V" shaped rims in favor of more "Oval" shaped rims.

Since another major complaint about aero tubing is the harshness (mainly due to the huge width of the mast, and many manufacturers are working on the mast to help resolve that issue, although Giant's new bend near the cluster is a total aesthetic disaster), so a less wide mast will be a bit easier on my butt as well.

Therefore, a rounder back half of the mast will increase the stiffness, use less material (no need to be as wide) with little compromise in aerodynamics.

The result, is an "egg" shaped tubing, for variously parts of the frame, and especially the seat mast, which will likely be around 35mm wide or less, and hopefully won't beat up my backside.

Therefore, a rounder back half of the mast will increase the stiffness, use less material (no need to be as wide) with little compromise in aerodynamics.

The result, is an "egg" shaped tubing, for variously parts of the frame, and especially the seat mast, which will likely be around 35mm wide or less, and hopefully won't beat up my backside.

It may behoove you to look at the rim shapes used by Zipp for heir firecrests, Flo Cycling's rim shapes, Trek's speed concept shape, etc. instead of just drawing an oval. You could scale them up to a given width and then "chop" the tail off to whatever your desired depth of the tube is.

I think you'll find that the "oval" shape found on aero wheels is due to the fact that the leading and trailing edges swap throughout the rotation and need to perform both roles.

However I like what you are doing with this and I think that with all the turbulence that would be found back at the seat post, an ellipse is a good option when considering structure as well as aerodynamics.

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